Advice on combi pressure loss please

[silver50]

Non condensing Vokera Linea plus boiler

I have had a GSR engineer out twice, yesterday and friday. The remit was service/check over and hopefully solve a degree of pressure loss. Unfortunately after doing this and pressurising the expansion vessel my pressure loss problem is WORSE!!! It used to take about ten days drop 1.5 bar with heating on a lot, now literally ten hours.

Yesterday he replaced the safety valve. Still the same. Accessing the back of the property is difficult but today I will try to look, just to see if any sign of water passing or indeed sign of any ongoing water passing. It's an upper flat and to the best of my knowledge no sign of a bad leak/reports from downstairs neighbour.

About 2 years ago I was told the main heat exchanger had a slight leak, this was when I started to become aware the system wasn't holding pressure as it used to. I just lived with it on the assumption it wasn't doing any harm. I remember getting shown the leak by this (different) GSR engineer but actually didn't see what he was talking about. The new engineer said we would soon know if it was the main HE. Is it at all possible this could still be the culprit, or on a non condensing boiler would water be seen, particularly with this extent of pressure loss?

This is starting to feel like an expensive nightmare. I can't believe nor explain the problem becoming worse!

 

[dilalio]

You need to ascertain if the pressure loss is from your boiler or from your heating system.
There are plenty of references in the archives and the 'net, but in short...

Turn boiler off; pressurise system; isolate boiler from system at flow and return connnections under boiler; wait 12 hours or so; check gauge on boiler if holding not boiler; open flow and return valves; if gauge drops then loss/leak is on CH system.

 

[silver50]

Thanks. Certainly looks like have to get engineer back.

The boiler is pressuring up a lot quicker just now. It definately took a lot longer to fill when I have had to top it up before. Does that mean anything or point to anything at all?

Sort of like it's going down in pressure more quickly, but also pressurising up more quickly.

 

[Madrab]

With the Expansion vessel re-pressurised then the system will respond to adding pressure more quickly. @dilalio testing process should identify if there is a leak in the boiler/HE and TBH your engineer should have been doing that to start with. I assume your engineer checked the blow off valve outside and decided it needed replaced as it was passing water?

 

[durhamplumber]

wasting your money repairing it.Fit a new boiler.

 

[silver50]

wasting your money repairing it.Fit a new boiler.

With due respect, this is in the first instance about finding out the cause of the pressure dropping, more so the last few days which appears somewhat inexplicable.

I have just checked outside the building and no sign of water passing. No sign of an actual blow off pipe though

Looks then a bit like either the heat exchanger or an under floor leak. Would it be true it's highly unlikely to be the heat exchanger without seeing water escape?

 

[silver50]

With due respect, this is in the first instance about finding out the cause of the pressure dropping, more so the last few days which appears somewhat inexplicable but has happened directly after the engineer visited.

I have just checked outside the building and no sign of water passing.

 

[Madrab]

If the primary HE is leaking then it then gets into the realms of 'is it economically viable' to repair what is an old boiler but personally I wouldn't be condemning it quite yet until fault is known.

 

[silver50]

With the Expansion vessel re-pressurised then the system will respond to adding pressure more quickly. @dilalio testing process should identify if there is a leak in the boiler/HE and TBH your engineer should have been doing that to start with. I assume your engineer checked the blow off valve outside and decided it needed replaced as it was passing water?

Sorry, missed your reply. No, he didn't actually check outside. It is a bit difficult to access. However my own check just now revealed no sign of a blow off pipe on the building. Could it be built into/beside flue?

 

[silver50]

Thanks for help Madrab

What do you think the chances are of fair leak at primary heat exchanger without seeing water dripping etc? This of course not a condensing boiler.

I thought I might've found a possible fault this morning, but seems not. I found a tap under my floorboards which allows draining the radiators down and it joins the blow off pipe. I thought the tap wasn't tight closed but unfortunately 2.5 hours later, still a pressure drop

 

[Madrab]

The blow off (PRV) pipe could be located within the building and connected to a waste somewhere but if that's the case then there should be a visible connection (tundish) to allow any water release to be visible. Where does the joined drain/blow off pipe run to then, can you follow it? Have you performed @dilalio 's test?

 

[silver50]

I've got the engineer coming back later so assume he'll (and I can of course suggest) isolate the heating.

I found the pipe outside, it was lower down wall than I expected. There is a drip sitting at the end of it (and I can't be 110% sure my tweaking the tap I found didn't release a wee bit water) but it's certainly not dripping as the kind of pressure drop i'm experiencing would produce. No tundish unfortunately but I now see how it's been installed (with the above tap joining the heating system to the blow off under floor to drain system down).

What do you think about a fairly substantial heat exchanger leak not being easily spotted? I was told this morning no sign of one (contrary to what I was told a year or two ago)

 

[dilalio]

OP: stop thinking large amounts of water! A typical sealed system doesn't need to lose a lot of water in order for the pressure to drop on the gauge!

 

[mcmoby69]

Did your registration check if the pipe that connects the expansion vessel is clear?

 

[silver50]

OP: stop thinking large amounts of water! A typical sealed system doesn't need to lose a lot of water in order for the pressure to drop on the gauge!

I had read that if losing 1.5 bar in a short space of time ie 8 hours then this would equate to 5L of water. Is that not necessarily the case?

There seems to be something odd going on. When I turned on all rads in house earlier (CH system already running 2 radiatirs all morning) the pressure increased by 1.5 bar. Conversely this evening I turned the TRVs off on most radiators and the pressure went down to nil. Had to fill again to get it going.

I'm sure I've never seen anything like the above difference in pressure in the past, and it certainly hadn't made the pressure drop out entirely within a few hours

Re above I'm not sure if the GSR checked pipe to expansion vessel clear. Was certainly whooshing and gurgling noises this eve when pressure went down again if that means anything